Abstract
The captive population of the maned wolf (Chrysocyon brachyurus) in the United States has an alarmingly high prevalence of cystinuria, a metabolic disorder that has proven to have an autosomal recessive mode of inheritance in both humans and domestic dogs.3-5,7 Previous research on the nutritional management of cystinuria in maned wolves2 led to the development of a commercially manufactured maintenance maned wolf diet that had been fed to almost all of the maned wolves in the United States since 1998. In an effort to make further improvements on this diet, an experimental diet was developed which was demonstrated to significantly raise the urine pH in the maned wolves tested.6 This study was performed in an effort to assess the long-term effects of this experimental diet vs. the commercially available manufactured diet on the overall nutritional and health status of the captive maned wolf.
Six adult maned wolves (three males, three females), maintained at the National Zoological Park’s Conservation and Research Center, were used in the study. For 14 weeks, two pairs of maned wolves were maintained on the commercially available maintenance diet, while two individually housed wolves were maintained on the experimental diet. All six wolves, both at the beginning and at the end of the diet trial, had severely decreased plasma levels of taurine (as compared to the normal canine reference range of 60–120 nmol/ml),1 with average taurine levels of 16 nmol/ml at the beginning of the study and 3 nmol/ml at the end of the study. There was no statistically significant difference in the taurine levels between animals on the maintenance vs. experimental diets. After receiving the taurine results following the trial, both diets were immediately supplemented with taurine at a level of 0.3%. All study animals were eventually switched to the taurine-supplemented version of the commercially manufactured maintenance diet, and subsequent samplings were performed to monitor plasma taurine levels. A final sampling, performed approximately 5 months following the initiation of taurine supplementation, revealed an average taurine level within the target canine reference range (90.25 nmol/ml), although two individuals continued to exhibit levels below the reference range. There are numerous physiologic (e.g., possible unique metabolism and requirements for taurine in this species as compared to other canids) and dietary factors (e.g., effects of the types and levels of both fiber and protein on nutrient availability, taurine metabolism, and enterohepatic circulation of taurine-conjugated bile salts; impaired taurine synthesis secondary to low cysteine availability) that could be potential contributors to the development of taurine deficiency in the maned wolves in this study.
Literature Cited
1. Amino Acid Analysis Laboratory. Department of Molecular Biosciences, School of Veterinary Medicine, University of California at Davis, Davis, CA.
2. Boniface, J. 1998. Dietary control of cystinuria in maned wolves (Chrysocyon brachyurus). Master’s thesis. University of Maryland, College Park, MD.
3. Bovee, K.C., and M. Bush. 1978. Cystinuria in the maned wolf. Nutr Pathol. 11: 121–125.
4. Bovee, K.C., M. Bush, J. Dietz, P. Jezyk, and S. Segal. 1981. Cystinuria in the maned wolf of South America. Science. 212: 919–920.
5. Casal, M.L., U. Giger, K.C. Bovee, and D.F. Patterson. 1995. Inheritance of cystinuria and renal defect in Newfoundlands. J. Am. Vet. Med. Assoc. 297(12): 1585–1589.
6. Childs-Sanford, S.E. and R. Angel. Effects of dietary protein source and dietary sodium to potassium ratio on urine pH and urine cysteine excretion in the maned wolf, Chrysocyon brachyurus. Submitted for publication.
7. Rosenberg L., J. Durant, Albrecht I. 1965. Intestinal absorption and renal excretion of cystine and cysteine in cystinuria. N. Engl. J. Med. 273: 1239–1345.